Islamic State (IS) militants have reportedly carried out execution-style killings of at least 30 Sunni tribesmen in Iraq's western Anbar Province.

Local officials said the killings took place on October 29 in Hit, a town that fell to IS militants earlier in October about 140 kilometers west of Baghdad.

Anbar Provincial Council Chairman Sabah Karhout said those who were executed were from the Al-Bou Nimr tribe, which is siding with government forces attempting to recapture territory seized by IS militants during the summer.

Officials say the killings are likely aimed at discouraging resistance against IS fighters from other Sunni tribes, which is critical for government forces to regain territory in Anbar Province.

IS militants did not immediately claim responsibility for the killings, but its fighters previously have executed hundreds of people in Iraq and Syria -- sometimes decapitating their victims and putting their heads on public display.

Meanwhile, a monitoring group says IS insurgents freed 25 Syrian Kurdish school children on October 29. They were the last children to be released out of more than 150 kidnapped in May.

The British-based Syrian Observatory for Human Rights, which tracks the civil war in Syria, said the children were released from the Syrian town of Minbij.

IS jihadists, who have been fighting Kurdish militia in Syria and Iraq, abducted the children aged 13 and 14 from the Syrian town of Kobani as they returned from taking exams in the city of Aleppo.

In subsequent weeks , several children escaped, while others were released in batches or individually.

The observatory says that, in September, IS released the largest batch of 70 children.

The releases come despite ongoing clashes between IS and Kurdish forces for control of Kobani.